Cod liver oil
A traditional three-in-one: omega-3 EPA+DHA, vitamin D, and vitamin A from the liver of cod. Particularly useful for those who already need D and A.
Strong evidence for the individual components (omega-3, D, A). The combined cod-liver-oil RCT evidence is most established for childhood respiratory infections, joint pain in RA, and as a winter vitamin D source. Effects: 4–8 weeks.
Cod liver oil was the original 'health tonic' before the modern supplement industry existed. The liver of cold-water cod stores significant vitamin A, vitamin D, and the long-chain omega-3s EPA and DHA — making cod liver oil a unique all-in-one. It's especially relevant in winter (less sun → less vitamin D), for those with limited fish intake, and as part of traditional dietary protocols (Weston A. Price, Scandinavian customs). Watch the A content — too much vitamin A becomes a concern with daily long-term use.
- Form
- Fermented cod liver oil (Green Pasture is the well-known brand — traditionalists' favourite). Standard cod liver oil from reputable brands (Carlson, Nordic Naturals — pleasantly flavoured). Check the label for vitamin A and D content per serving.
- Dose
- 1 teaspoon to 1 tablespoon daily, depending on product strength. Read the label for vitamin A — keep total daily intake (including from food and multivitamins) under 10,000 IU.
- Timing
- With a fat-containing meal. AM typical.
- Schedule
- Daily, especially in winter months. Some traditional protocols cycle off in summer when sun exposure provides D.
- Side effects
- Fishy aftertaste. Mild GI upset. Vitamin A toxicity at high chronic doses (headache, dry skin, hair loss).
- Interactions
- Anticoagulants — mild additive (omega-3). Acne retinoids (isotretinoin) — additive vitamin A toxicity. Other vitamin A or D supplements — total it all up to stay in range.
- Contraindications
- Pregnancy (>10,000 IU vitamin A is teratogenic — most cod liver oil products are OK at standard doses, but check). Hypervitaminosis A or D. Hemochromatosis.
- Lab markers
- 25-OH-D, omega-3 index, lipids. Serum retinol if running high-dose long-term.
- Food sources
- Cod liver oil IS a food in many traditions. The closest food equivalent is eating the livers of cold-water fish directly (cod, halibut, salmon).
Pairs with
Vitamin K2 (mandatory partner to any vitamin D source — routes calcium to bone, not arteries). Vitamin E (protects the omega-3 fats from oxidation). Magnesium (for D activation).
Where to buy
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within Fatty acids